The Disclaimers of Open Data

We're faced in an age now, aren't we, where whatever you subscribe to or buy, you're faced with huge disclaimers. I probably look at those disclaimers more for open data than I do for other things. In part because my business is based around supplying it and processing of open data, I need to know whether or not it's fully open. So are there levels of openness? Because this is something that bugs me quite a bit: if you have to log in and create an account and provide details, is that pure open data? Whether the quality of it will be good, whether you can find it will be another significant issue. And how accessible it is that we